Add health check to Dockerfile for SSH daemon

This update introduces a HEALTHCHECK instruction to the Dockerfile, ensuring that the SSH daemon is running properly. The health check runs every 30 seconds and verifies the process is active, enhancing the reliability of the Docker image.

Author: jaydrogers

src/Dockerfile

@@ -53,6 +53,8 @@ LABEL org.opencontainers.image.title="serversideup/docker-ssh" \
     org.opencontainers.image.version="${REPOSITORY_BUILD_VERSION}" \
     org.opencontainers.image.licenses="GPL-3.0-or-later"
 
+HEALTHCHECK --interval=30s --timeout=30s --start-period=30s --retries=3 \
+    CMD pgrep -f "sshd.*-D" > /dev/null || exit 1
 
 ENTRYPOINT ["/usr/bin/tini", "--", "/entrypoint.sh"]
 CMD ["/usr/sbin/sshd", "-D", "-e"]